Mask electrode support for color picture tube

ABSTRACT

A color picture tube in which a color selective mask is supported by mask support means made of a plurality of elastic material sheets each shaped and arranged so as to have a relatively large elasticity in a direction being in a plane parallel to a side face of a mask frame to which the sheet is secured and perpendicular to the length of the side face, thus serving as a torsion spring, so that the path of local displacement of the color selective mask and its peripheral frame due to thermal expansion or their displacement due to any external force is substantially coincident with the path of a deflected electron beam, thereby compensating for the deviations of relative positions between phosphor dots and corresponding apertures in the mask.

United States Patent 1191 Yamazaki 1 MASK ELECTRODE SUPPORT FOR COLOR PICTURE TUBE [75] Inventor: Eiichi Yamazaki, lchihara, Japan [73] Assignee: Hitachi, Ltd., Tokyo, Japan [22] Filed: June 30, 1972 [21] Appl. No.: 268,111

[30] Foreign Application Priority Data 1 Aug. 27, 1974 3,601,650 8/1971 Pappadis 313/292 x Primary EraminerHerman Karl Saalbach Assistant ExaminerSiegfried H. Grimm Attorney, Agent, or FirmCraig & Antonelli ABSTRACT A color picture tube in which a color selective mask is supported by mask support means made of a plurality of elastic material sheets each shaped and arranged so as to have a relatively large elasticity in a direction being in a plane parallel to a side face of a mask frame to which the sheet is secured and perpendicular to the length of the side face, thus serving as a torsion spring, so that the path of local displacement of the color selective mask and its peripheral frame due to thermal expansion or their displacement due to any external force is substantially coincident with the path of a deflected electron beam, thereby compensating for the deviations of relative positions between phosphor dots and corresponding apertures in the mask.

6 Claims, 11 Drawing Figures mamas 182 3.832.592

MB 1 if 2 PRIOR ART MASK ELECTRODE SUPPORT FOR COLOR PICTURE TUBE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to color picture tubes and, more particularly, to those having mask support means for supporting within the panel portion a mask frame as well as a color selective mask carried by the mask frame.

2. Description of the Prior Art As color picture tubes the shadow-mask color picture tubes are presently most widely used. Usually, this type of color picture tube consists of a neck portion accommodating electron gun means producing three electron beams respectively responsible for red, green and blue colors, a funnel portion flaring forwardly from the neck portion, and a panel portion provided with a phosphor screen consisting of red, green and blue phosphor dots regularly arranged into a mosaic form and accommodating a removably disposed shadow mask assembly facing the phosphor screen.

The shadow mask assembly usually consists of a shadow mask or color selective mask provided with fine apertures through which electron beams emitted from the electron gun means are admitted to pass, a mask frame carrying the color selective mask, and mask support means secured to the mask frame and adapted to be fitted to support pins extending from the inner wall surfaces of the panel. The mask support means chiefly consists of a plurality of elastic leaf spring members, each secured at one end to the mask frame and at the other end to a corresponding support pin to thereby support the color selective mask within the panel portion of the tube.

In the color picture tube of the above construction, as the color selective mask and its frame undergo thermal expansion due to heat generated during its operation, for example, by bombardment of electrons, the position of the color selective mask relative to the phosphor screen, that is, position of the small apertures in the color selective mask relative to the corresponding phosphor dots of the phosphor screen, is deviated. In addition, the shadow mask assembly is very unresisting against any external shock that tends to move the color selective mask in a direction perpendicular to a side face of the mask frame. These apparently result in degradation of color purity and also resolution of the color image.

To cope with these drawbacks, it has heretofore been proposed to secure one end of each leaf spring member to the mask frame not directly but via a heat sensitive material such as a bimetal strip and the other end of the spring member to the support pin, thereby to compensate for the thermal expansion. This measure is fairly effective in compensating for the deviation of the relative position of the small apertures of the color selective mask with respect to the phosphor dots due to the thermal expansion of the color selective mask and its frame. However, the resistivity against external shocks of the above-mentioned nature is still so poor that the color purity of reproduced images and resolution has not yet been successfully improved.

SUMMARY OF THE INVENTION A primary object of the invention is to provide an improved color picture tube free from the aforementioned inconveniences.

Another object of the invention is to provide a color picture tube, which is less susceptible to external shocks and vibrations, and in which the mounting and removal of the color selective mask may be readily carried out.

In accordance with the invention, there is provided a color picture tube, which uses a mask support means constituted by a plurality of integral elastic sheet material members each secured to a different side face of a mask fame so as to have a sufficiently large elasticity in a direction being in a plane prallel to the side face and perpendicular to the length of the side face and a small elasticity in a direction perpendicular to the side face of the mask frame, said elastic sheet material being arranged such that the displacement of the color selective mask and its frame due to thermal expansion takes place along the same paths as for deflected electron beams emitted from the electron gun means, thereby compensating for the deviation of relative positions between color selective mask apertures and corresponding phosphor dots.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view, partly in section, showing a usual shadow-mask color picture tube.

FIG. 2 is a fragmentary perspective view showing an example of the prior-art mask support structure.

FIG. 3 is a fragmentary sectional view to illustrate electron beam landing error due to thermal expansion of the color selective mask and its frame in the prior-art color picture tube.

FIG. 4 is a fragmentary perspective view showing another example of the prior-art mask support means.

FIG. 5 is a fragmentary perspective view showing an embodiment of the invention.

FIG. 6 is a fragmentary sectional view to illustrate the effect of canceling the electron beam landing error due to thermal expansion in the color picture tube according to the invention.

FIG. 7 is a view similar to FIG. 5 showing another embodiment of the invention.

FIGS. 8a and 8b show a further embodiment of the invention.

FIGS. 9a and 9b show a still further embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With a view to facilitating the understanding of the present invention, brief explanation will first be made to prior-art structures with reference to FIGS. 1 to 4.

FIG. 1 shows a shadow-mask color picture tube consisting of a neck portion 3 accommodating an electron gun 2, a funnel portion 4, and a panel portion 7 accommodating a color selective mask 61 and a phosphor screen 5. The mask 61 is mounted on a mask frame 62 and is held in position by mask support means 63 each having a hole receiving a support pin 8 provided on the inner walls of the panel portion 7.

The mask support means 63 usually has a construction as shown in FIG. 2. It consists of a plurality of leaf spring members each having an end portion welded to the mask frame 62 at positions labeled with cross marks and the opposite end portion provided with a hole 64 receiving an associated support pin 8.

With the prior-art color picture tube of the above construction, the color selective mask 61 and its frame 62 undergo thermal expansion due to electron bombardment, resulting in local displacement to positions 61a and 62a as shown by broken lines in FIG. 3. Therefore, while the electrom beam 1 strikes the center of the phosphor dots (not shown) during a certain initial period from the start of the operation of the tube, the position of the electron beam landing gradually deviates from the phosphor dot center with lapse of time, resulting in deterioration of the color purity. Further, the leaf spring member 63 is yielding to an external force in a direction perpendicular to a side face of the mask frame.

To overcome this problem, there has been proposed and adopted a mask support means as shown in FIG. 4. In this structure, the leaf spring member 63 is secured to the mask frame 62 not directly but through a thermal expansion compensating material 10, for instance a bimetal strip, which is welded to the mask frame 62. This electron beam landing error due to the thermal expansion of the color selective mask 61 and its frame 62 is of such nature that it would be completely canceled if the local displacement of the mask 61 and its frame 62 due to their thermal expansion causes the small apertures formed in the mask to undergo displacement along the path of deflected electron beams. Accordingly, it is desirable to determine the shape, material and location of the spring member 63 on the basis of the above principle. However, the aforementioned mask support means is still unresisting against such inconveniences as mentioned above and that the color selective mask and its frame are yielding to vibrations transmitted to them during operation. The same is true of a case where the thickness and width of the leaf spring are increased since the elasticity in a direction perpendicular to the length of a side face of a mask frame on which the leaf spring member is secured would be reduced so that the installation and removal of the mask frame becomes extremely difficult. Also, since in such a case very strong force acts upon the support pin, it is prone to some displacement as the temperature of the support pin is elevated during the assembling process. Further, the incorporation of the bimetal strip as expansion compensating means not only makes the design of the leaf spring difficult but also leads to such economical disadvantages that the bimetal strip itself is expensive and that an extra process of welding is required.

FIG. 5 shows an embodiment of the color picture tube, particularly a mask support means, according to the invention. In the Figure, reference numeral 12 designates a leaf spring member made of a rectangular elastic sheet. The mask support means consists of a plurality of, for example, three or four leaf spring members. Hereinafter, only one member will be described for convenience. It includes bonding end sections b and C intermediate parallelogrammic leg sections 01 and e extending from ends of the bonding sections b and c and a central engaging section g bridging the intermediate sections (1, and e and provided with a central hole f receiving a support pin not shown. The sections b d g e and constitute a single continuous body. The bonding end sections b and 0 of the leaf spring member 12 are bonded to a side face of the mask frame 62 by means of welding, for instance spot welding. Thus, the intermediate sections 11 and e extend outwardly and downwardly toward the tube neck from the face of the mask frame 62 as can be seen from FIGS. 5 and 6. By this arrangement, the section 812 including the hole f g is positioned further from the phosphor screen (not shown) than the sections b and The effect of canceling the electron beam landing error achieved in accordance with the invention will now be discussed with reference to FIG. 6 wherein the shadow mask assembly is fixed in position with the support pins 8 engaged with the holes f of the engaging section of the spring members 12 of FIG. 5. When the tube is in operation, the color selective mask 61 and its frame 62 initially in their respective locations of solid lines undergo thermal expansion due to the bombardment by an electron beam 1. At this time, the leaf spring member 12 (Hereinafter, only the indicated member 12 and associated portions will be referred to.), which has its end sections b and c bonded to a side face of the mask frame 62, acts as a kind of torsion spring. Thus, as the color selective mask 61 and its frame 2 undergo thermal expansion, they are locally displaced or shifted along paths shown by arrow A with respect to the leaf spring central hole f in engagement with the support pin 8 to assume respective positions 61a and 62a as indicated by broken lines. The path along which the maskand its frame are locally displaced is made to substantially coincide with the path for deflected electron beams passing through any corresponding small aperture in the mask 61. Thus, the deviation of the position of landing of the electron beam 1 from the phosphor dot center, can be substantially compensated for to cancel the electron beam landing error. Furthermore, due to the above-described specific arrangement and shape of the spring member, any external force that tends to move the color selective mask in a direction perpendicular to the side face of the mask frame results in the displacement in the direction indicated by arrow A.

FIG. 7 shows a modification of the mask support means described above. It consists of a leaf spring member 13 having bonding end sections b and 0 bonded to a side face of the mask frame 62 and intermediate leg sections d and e extending outwardly from the side face of the mask frame 62 as indicated and a central engaging section gm bridging the intermediate sections d and e and provided with a downward or rearward protrusion h extending substantially parallel to the side face of the mask frame 62, the protrusion having a hole f The sections b d g e and 0, constitute a single continuous body.

FIGS. 8a and 8b show a further mask support means embodying the invention. It consists of a leaf spring member 14 having opposite end sections b and C bonded to a side face of the mask frame 62 and a central section integral with an intermediate leg section d extending outwardly and downwardly toward the tube neck from the side face of the mask frame 62 and an engaging section g provided with a hole f The sections b c d and g constitute a single continuous a central section integral with an intermediate leg section d extending outwardly and downwardly toward the tube neck from the side face of the mask frame 62 and an engaging section g provided with a hole f The sections I7 d and g constitute a single continuous body.

Like the leaf spring member of FIG. 5, those of FIG. 7 to FIGS. 9a and 9b have the opposite end sections bonded to a side face of the mask frame 62. They act as torsion springs so that the manner of displacement of the color selective mask and its frame will be made coincident with the path for deflected electron beams. It should be noted that the above-mentioned downward and outward directions of extension of the intermediate sections d e (FIG. 5); d (FIGS. 8a and 8b); and d (FIGS. 9a and 9b) are such that they continue from the bonding sections b 0, b c and b 0, and extend away from the associated side face of the mask frame 62 and away from the phosphor screen, thereby the holes in the engaging sections are further from the phosphor screen than the bonding sections.

While the foregoing description is concerned with the shadow-mask color picture tube, the invention is by no means limited thereto, but it may be quite equally applied to the gridtype color picture tubes such as chromatrons.

I claim: I

I. In a color picture tube including electron gun means, an envelope having a neck portion accommodating said electron gun means, a funnel portion and a panel portion provided with a phosphor screen on the inner surface thereof, a color selective mask mounted on an annular mask frame and mask support means for supporting said mask frame on said panel portion to position said color selective mask in place in front of said screen within said envelope, the improvement comprising a mask support means forming a torsion spring which includes a plurality of integral flexible sheet spring sections each consisting of opposite end sections bonded to different points spaced circumferentially along the surface of said mask frame, at least one intermediate leg section extending from said end sections away from said surface of said mask frame and away from said phosphor screen and an engaging section extending from said one intermediate leg section substantially parallel to said surface of said mask frame and provided with a hole, the axis of said hole in said engaging section being in a first plane transverse to the axis of said tube and intersecting said tube axis at a first point, and all corresponding bonding points of said opposite end sections at which they are bonded to said surface of said mask frame being in second planes substantially parallel to said first plane and intersecting said tube axis at second points, said first point being further from said phosphor screen than said second points, whereby each said integral sheet serves as a torsion spring.

2. The color picture tube according to claim I in which said each integral elastic sheet has two intermediate leg sections of a parallelogrammic form and said engaging section bridges said two parallelogrammic intermediate leg sections.

3. The color picture tube according to claim 1 in which each integral elastic sheet has two intermediate leg sections and said engaging section bridges said two intermediate sections, said engaging section having a protrusion extending in a direction away from said phosphor screen and parallel to the axis of the color picture tube and said hole being formed in said protrusion.

4. The color picture tube according to claim 1 in which said each integral elastic sheet has one intermediate leg section and said end sections being united with a central section, said leg section extending from said central section.

5. The color picture tube according to claim 1 in which said each integral elastic sheet has a U-shaped section having a pair of leg members serving as said end sections to be bonded and a central section joining said leg members, the U-shaped sheet being bonded to the mask frame only at said leg members.

6. In a color picture tube including electron gun means, an envelope having a neck portion accommodating said electron gun means, a funnel portion and a panel portion provided with a phosphor screen on the inner surface thereof, a color selective mask mounted on an annular mask frame, and mask support means for supporting said mask frame on said panel portion coaxially with said electron gun means to position said color selective mask in place in front of said screen within said envelope, the improvement comprising a mask support means which includes a plurality of flexible strips spaced about the periphery of said mask frame with an orientation transverse to the axis thereof, each strip being a one-piece member consisting of opposite end sections bonded to the surface of said mask frame, a pair of intermediate leg sections of non-rectangular parallelogrammic shape extending from respective ones of said end sections in directions away from said surface of said mask frame and away from said phosphor screen and an engaging section bridging said intermediate leg sections in a plane substantially parallel to said surface of said mask frame, said engaging section being provided with a hole for engagement by said panel portion, which hole is positioned further from said screen than the bonded portions of the end sec- 

1. In a color picture tube including electron gun means, an envelope having a neck portion accommodating said electron gun means, a funnel portion and a panel portion provided with a phosphor screen on the inner surface thereof, a color selective mask mounted on an annular mask frame and mask support means for supporting said mask frame on said panel portion to position said color selective mask in place in front of said screen within said envelope, the improvement comprising a mask support means forming a torsion spring which includes a plurality of integral flexible sheet spring sections each consisting of opposite end sections bonded to different points spaced circumferentially along the surface of said mask frame, at least one intermediate leg section extending from said end sections away from said surface of said mask frame and away from said phosphor screen and an engaging section extending from said one intermediate leg section substantially parallel to said surface of said mask frame and provided with a hole, the axis of said hole in said engaging section being in a first plane transverse to the axis of said tube and intersecting said tube axis at a first point, and all corresponding bonding points of said opposite end sections at which they are bonded to said surface of said mask frame being in second planes substantially parallel to said first plane and intersecting said tube axis at second points, said first point being further from said phosphor screen than said second points, whereby each said integral sheet serves as a torsion spring.
 2. The color picture tube according to claim 1 in which said each integral elastic sheet has two intermediate leg sections of a parallelogrammic form and said engaging section bridges said two parallelogrammic intermediate leg sections.
 3. The color picture tube according to claim 1 in which each integral elastic sheet has two intermediate leg sections and said engaging section bridges said two intermediate sections, said engaging section having a protrusion extending in a direction away from said phosphor screen and parallel to the axis of the color picture tube and said hole being formed in said protrusion.
 4. The color picture tube according to claim 1 in which said each integral elastic sheet has one intermediate leg section and said end sections being united with a central section, said leg section extending from said central section.
 5. The color picture tube according to claim 1 in which said each integral elastic sheet has a U-shaped section having a pair of leg members serving as said end sections to be bonded and a central section joining said leg members, the U-shaped sheet being bonded to the mask frame only at said leg members.
 6. In a color picture tube including electron gun means, an envelope having a neck portion accommodating said electron gun means, a funnel portion and a panel portion provided with a phosphor screen on the inner surface thereof, a color selective mask mounted on an annular mask frame, and mask support means for supporting said mask frame on said panel portion coaxially with said electron gun means to position said color selective mask in place in front of said screen within said envelope, the improvement comprising a mask support means which includes a plurality of flexible strips spaced about the periphery of said mask frame with an orientation transverse to the axis thereof, each strip being a one-piece member consisting of opposite end sections bonded to the surface of said mask frame, A pair of intermediate leg sections of non-rectangular parallelogrammic shape extending from respective ones of said end sections in directions away from said surface of said mask frame and away from said phosphor screen and an engaging section bridging said intermediate leg sections in a plane substantially parallel to said surface of said mask frame, said engaging section being provided with a hole for engagement by said panel portion, which hole is positioned further from said screen than the bonded portions of the end sections of the strip. 